The specification U.S. Pat. No. 6,605,899 B2 has disclosed a tubular barrier discharge lamp having linear inner electrodes. The inner electrodes extend along the entire inner wall of the discharge tube and are passed to the outside in a gas-tight manner at one end. For this purpose, the discharge tube is sealed in a gas-tight manner at the end of the electrode bushings with the aid of a closure element in the form of a plate. For this purpose, the discharge tube is provided at this end with a constriction which annularly surrounds the edge of the closure element in the form of a plate. The constriction and the closure element in the form of a plate are then fused with one another in a gas-tight manner, the inner electrodes being passed through this seal to the outside.
Such lamps having different lengths are required in many applications, for example for scanner areas of different sizes. For example, there are devices which are suitable for documents having a size of up to A3 but also others which are suitable for up to A2 or even up to A0. For this purpose, in each case different lamps having a corresponding length are required. In order in this case to ensure the same illuminance for lamps of different lengths, a correspondingly matched operating device is required for each lamp length. Specifically it has been shown that the illuminance is approximately halved when a lamp is operated which has a length of approximately 650 mm using the same operating device that is designed for a lamp having a length of approximately 350 mm.